The plan, with 1 smartphone and 6GB is $120. The same service with the unlimited plan is $120. Don't forget the $80 covers unlimited voice and text services - same as the $90/mo plan under the old system.
I pay $80 a month for unlimited data, 450 minutes (I never go over 50) and 1000 messages. I'm much more data-centric than voice/messaging. Switching plans makes no sense for me.